This single phase transformer calculator finds the turns ratio, secondary voltage, and current from your primary and secondary values. Enter the known figures above.
Formulas
Turns ratio a = Vp ÷ Vs = Np ÷ Ns Currents Ip ÷ Is = Vs ÷ Vp Rating VA = Vp × Ip = Vs × Is
Example
240 V → 120 V: turns ratio = 240 ÷ 120 = 2:1. At 1 kVA, secondary current = 1000 ÷ 120 = 8.3 A.
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Frequently Asked Questions
What is the turns ratio of a transformer?
It is the primary voltage divided by the secondary voltage, which also equals the ratio of primary to secondary turns.
How do I find secondary voltage?
Divide the primary voltage by the turns ratio, or multiply primary volts by secondary turns over primary turns.
Is current higher on the low-voltage side?
Yes. The low-voltage secondary carries proportionally more current, since VA is conserved.